Digital Sound & Music: Concepts, Applications, & Science, Chapter 6, last updated 6/25/2013
whatever is asked for in the MIDI messages. Because the sounds played are actual recordings of
musical instruments, they sound realistic.
The NN-XT sampler from Reason is pictured in Figure 6.18. You can see that there are
WAV files for piano notes, but there isn’t a WAV file for every single note on the keyboard. In
a method called multisampling, one audio sample can be used to create the sound of a number
of neighboring ones. The notes covered by a single audio sample constitute a zone. The sampler
is able to use a single sample for multiple notes by pitch-shifting the sample up or down by an
appropriate number of semitones. The pitch can’t be stretched too far, however, without
eventually distorting the timbre and amplitude envelope of the note such that the note no longer
sounds like the instrument and frequency it’s supposed to be. Higher and lower notes can be
stretched more without our minding it, since our ears are less sensitive in these areas.
There can be more than one audio sample associated with a single note, also. For
example, a single note can be represented by three samples where notes are played at three
different velocities – high, medium, and low. The same note has a different timbre and
amplitude envelope depending on the velocity with which it is played, so having more than one
sample for a note results in more realistic sounds.
Samplers can also be used for sounds that aren’t necessarily recreations of traditional
instruments. It’s possible to assign whatever sound file you want to the notes on the keyboard.
You can create your own entirely new sound bank, or you can purchase additional sound
libraries and install them (depending on the features offered by your sampler). Sample libraries
come in a variety of formats. Some contain raw audio WAV or AIFF files which have to be
mapped individually to keys. Others are in special sampler file formats that are compressed and
Figure 6.18 The NN-XT sampler from Reason
A synthesizer, if you use this word in the strictest sense, doesn’t have a huge memory
bank of samples. Instead, it creates sound more dynamically. It could do this by beginning with
basic waveforms like sawtooth, triangle, or square waves and performing mathematical